A NASA videograb on Saturday, March 21, 2009, shows space shuttle Discovery astronauts Joseph Acaba (L) and Steven Swanson complete second spacewalk.[Xinhua/AFP]
![A NASA videograb on Saturday, March 21, 2009, shows space shuttle Discovery astronauts Joseph Acaba (L) and Steven Swanson complete second spacewalk.[Xinhua/AFP]](http://images.china.cn/attachement/jpg/site1007/20090323/000bcdb95f1d0b3124e105.jpg "A NASA videograb on Saturday, March 21, 2009, shows space shuttle Discovery astronauts Joseph Acaba (L) and Steven Swanson complete second spacewalk.[Xinhua/AFP]")